The present invention relates to a stacked semiconductor device in which a plurality of wiring substrates each mounted with a semiconductor device are stacked to constitute a package and a semiconductor system in which the stacked semiconductor device is loaded.
For the purpose of attaining high packed density of semiconductor devices, a plurality of wiring substrates each mounted with a semiconductor device are often stacked one on another to constitute a stacked package. A conventional stacked package is constituted as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publications Nos. 9-219490, 10-135267 and 10-163414.
The conventional package is constituted as follows. First, individual packages such as a TSOP (thin small outline package), a TCP (tape carrier package) and a BGA (ball grid array) are each assembled completely. Then, the respective packages are stacked one on another through spacers with external terminals thereof being faced one another. These packages are thus formed integrally as a single stacked package. Finally, they are electrically connected to one another.
The conventional stacked package described above necessitates a processing step of stacking the individual packages in addition to a step of assembling the individual packages. Such a stacked package is manufactured by a sequential method in which the number of steps increases by the number of packages. This-method causes serious problems of increasing manufacturing cost and materials cost of spacers used for stacking a plurality of packages. FIGS. 12A to 13B illustrate a conventional stacked-type semiconductor device. Individual packages 104 and 106 each mounted with a semiconductor device, such as a TSOP, a TCP and a BGA, are assembled completely. These packages 104 and 106 are then soldered to a wiring substrate or module substrate 103 such as a printed board to complete a module. In the individual package 104 such as a TSOP, for example, an external terminal 105 of the semiconductor device is soldered to a metal wiring on the module substrate 103, and the substrate 103 is attached to an external device 110 constituted of a semiconductor system comprising semiconductor devices. In the case of FIG. 13B, the individual package 103 is mounted and connected on the substrate 103 by means of solder balls 107.
The external device 110 includes a spring terminal 101 made of a flat spring plate mounted on a substrate 100 which is further mounted on a base 102. The module substrate 103 is fitted to the external device 110 such that a connection terminal 108 of the substrate 103 contacts the spring terminals 101 of the external device 110.
The above example, however, has the problem that a soldering portion deteriorates as time passes due to a difference in thermal expansion coefficient between the package 104 or 106 and the module substrate 103. The connection terminal 108 is provided on the surface of the substrate 103 except where the package 104 or 106 is mounted, so that the entire module includes a package mounting section and a connection terminal section. It is thus too large as a module of a portable storage medium for use in small-sized personal computers, portable terminals, and voice recorders.
Once a module is mounted on a system, melting solder of a connecting portion by heat and replacing the module with another module is required, which is like to cause poor connection. In the prior art structure, it is impossible to remove only a desired module from the system and insert another therein.
The foregoing prior art semiconductor device has the problem that it does not produce an electric field shielding effect sufficiently.
As a semiconductor device increases in density and decreases in thickness and is used widely in IC cards and cellular phones, for example, a thin stacked package which is suitable for a semiconductor chip having a thickness of about 30 xcexcm to 200 xcexcm will be required in the future.
The present invention has been developed in consideration of the above situation and its object is to provide a stacked semiconductor device which is thin, high in heat radiation, excellent in shield effect and easy to attach/detach to/from an external system, and a semiconductor system mounted with the stacked semiconductor devices.
A stacked semiconductor device according to one aspect of the present invention comprises a plurality of stacked wiring substrates each including a plurality of via-holes in which connection electrodes are buried and wires electrically connected to the connection electrodes, an uppermost wiring substrate stacked on a top of the stacked wiring substrates and including a plurality of via-holes in which connection electrodes are formed and wires electrically connected to the connection electrodes, a semiconductor device mounted on each of the wiring substrates and electrically connected to the wires thereof, a plurality of conductive via insulation substrates each having a chip cavity which is larger than the semiconductor device enclosed therein and each including a plurality of via-holes in which connection electrodes are buried, each of the conductive via insulation substrates being inserted between two wiring substrates, and a plurality of conductive layers formed on a top surface of the uppermost wiring substrate and/or a bottom surface of a lowermost wiring substrate formed under the stacked wiring substrates, wherein the wiring substrates, the uppermost wiring substrate, and the conductive via insulation substrates are electrically connected to each other by the connection electrodes.
The conductive layers can be used as external connection terminals. Each of the external connection terminals may have a diameter of 1 mm or more and an area of 1 mm2 or larger.
At least one of the connection electrodes of the wiring substrates, the uppermost wiring substrate, and the conductive via insulation substrates can be connected to a ground line, and at least one of the conductive layers can electrically be connected to the ground line through the connection electrodes. At least one of the conductive layers may serve as a heat radiation layer. The area of the conductive layers occupying one of the uppermost wiring substrate and the lowermost wiring substrate may range from 50% to 95% of the whole surface area of the uppermost or lowermost wiring substrate. The via-holes of the wiring substrates, the uppermost wiring substrate, and the conductive via insulation substrates can be exposed to sides of the substrates, in such a manner that the connection electrodes buried in the via-holes are exposed to side walls of the substrates. The connection electrodes exposed to the side walls of the substrates may serve as external connection terminals. The semiconductor device may have a thickness of 30 xcexcm to 200 xcexcm.
The plurality of conductive layers formed on the top surface of the uppermost wiring substrate and the underside of the lowermost wiring substrate are used as heat radiation layers, external connection terminals and shield layers. When the conductive layers are used as external connection terminals, they are connected to the connection electrodes connected to a signal line in the package. When the conductive layers are used as shield layers, they are connected to a ground line. The shield layers and the external connection terminals can be arranged on one of the uppermost or undermost wiring substrate, and the shield layers and the external connection terminals can be used also as the heat radiation layers. The conductive layers can be used only as the heat radiation layers.
A semiconductor system according to another aspect of the present invention comprises external connection terminals of the semiconductor device including spring terminals made of flat spring plates. The plurality of conductive layers are formed on the top surface and/or the bottom surface of the uppermost or lowermost wiring substrates. A stacked semiconductor device of the present invention, which is thin, high in heat radiation, excellent in shield effect, and easy to attach/detach to/from the external device, can thus be attained, and so can be mounted to a semiconductor system easily.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.